1. Field of the Invention
This invention relates to a center pivot irrigation system and more particularly to a moisture activated control for the center pivot irrigation system.
2. Description of the Prior Art
Center pivot irrigation systems are made up of an irrigation arm extending radially outward from a center pivot. When activated the irrigation arm rotates over a period of time around the pivot thereby watering the area that the arm passes over. The length involved in a 360 degree rotation of the irrigation arm may be up to several days.
The center pivot system is generally driven by electric motors and may include a pumping system to control the pressure of the water supply. The control of known systems may be either manual or semiautomatic. A farmer is required to start and stop the system by going to the system controller and manually actuating control switches. It is known to provide the system with a limit switch activated by the position of the irrigation arm in order to shut down the system. The limit switch is usually mounted on the center pivot and is activated by a stop cam on the radial arm of the center pivot. The limit switch must be set manually each time the farmer wants to stop the system. Once the limit switch is set the most the pivot can rotate would be a single revolution. Because of the limited range of this type of semi-automatic shut-off, the farmer is often required to make a separate trip into the field to either restart the system after it has been stopped or set the limit switch to stop when he feels the field is sufficiently watered.
Another feature of known irrigation systems is a pressure safety shut-off switch. This services to shut down the system when water pressure is lost, due to for example pump failure or a power outage. A further disadvantage of the known system is that this pressure safety switch must be manually overridden when starting the system because there is no pressure in the water supply at the start of operation.
The known center pivot systems require near constant attention by a farmer. He must carefully pay attention to the soil and weather conditions in order to determine when and how much to water. A great amount of waste occurs in the pumping, power, and water costs, when a field is overwatered. Known systems further result in high fertilizer costs due to leaching as well as high farmer transportation costs, i.e., pickup trucks to transport the farmer to the controller and maintenance of transportation and the irrigation system itself.